Method of and apparatus for forming frangible casting molds



Feb. 3, 1959 L. R. SCHILLINGY METHOD OF AND APPARATUS FOR FORMING FRANGIBLE CASTING MOLDS Filed Sept. 1. 1954 6 Sheets-Sheet l INVENTOR Lewis R. Schilling BY W 7 (27/ ATTORNEYS Feb. 3, 1959 R. SCHILLING METHOD OF AND APPARATUS FOR FORMING FRANGIBLE CASTING MOLDS Filed Sept. 1, 1954 6 Sheets-Sheet 2 gg dqg Qua;

INVENTOR Lewis R. Schilling BY 5mm F7z 6 7 ATTORNEYS Feb. 3, 1959 L. R. SCHILLING 2,871,528

METHOD OF AND APPARATUS FOR FORMING FRANGIBLE CASTING MOLDS Filed Sept. 1, 1954 6 Sheets-Sheet 3 iNVENTOR Lewis R.Schilling ATTORNEYS Feb'. 3, 1959 L. R.SCHILLING 2,871,528

METHOD OF AND APPARATUS FOR FORMING FRANGIBLE CASTING MOI-D5 Filed Sept. 1, 1954 6 Sheets-Sheet 4 5 0 INVENTOR 4 Lewis R. Sqkilling F1 15 I BY w 7 ATTORNEYS Feb. 3, 1959 L. R. SCHILL'ING 2,871,528

METHOD OF AND APPARATUS FOR FORMING FRANGIBLEI CASTING MOLDS Filed Sept. 1, 1954 s Sheets-Sheet 5 m m INVENTOR Lewis R.Schilling ATTORNEYS Feb. 3, 1959 L. R. SCHILLING METHOD OF AND APPARATUS FOR FORMING FRANGIBLEI CASTING MOLDS 6 Sheets-Sheet 6 Filed Sept. 1, 1954 INVENTOR Lewis B. Schilling f77 ATTORNEYS United States w F METHOD OF AND APPARATUS FOR FORM ING FRANGIBLE CASTING MOLDS I Lewis R. Schilling, Shaker Heights, Ohio, assignor tt Kolcast Industries Inc., Cleveland, Ohio, a corporatiol of Ohio This invention relates to an improved method of forming frangible one-piece casting molds by making a'fusible pattern which conforms to the article to be cast, investing the same in a suitable mold forming material, and fusing the pattern to remove it from the investing material and provide a casting cavity.

In forming molds by the investment method a pattern -of fusible material is made that conforms accurately to the article to be cast and, in order to obtain aperfect casting, it is necessary to avoid distortion of the pattern during the assembly of the pattern parts and during investit is also necessary to prevent any marring of the investing material in the handling thereof incident to the fusion of the pattern and the discharge of the fusible materialmay be present in the material forming the fusible pattern.

In forming molds by the method of the present invention, a pattern composed of a low melting point mate- '25 .ment of the pattern with the mold forming material and rial is accurately formed to a size and shape correspond- I ing to that of the article to be cast and this pattern is supported during the investing and fusing operations by a carrier formed of a material of higher melting point than the pattern and rigidly attached to the pattern. The portion of the carrier attached to the pattern is provided with a covering layer of low melting point material that is integrally joined to the pattern by spaced gate forming risers of low melting point material that -areintegrally joined at one end to-the pattern and at the other end to the covering layer on the carrier. After the pattern and carrier are assembled and joined together, the pattern and the portion of the carrier attached thereto'are invested 1 with a shell of the mold forming material, after which the investing layer is removed from the side of the at tached part of the carrier that faces away from the pattern. After the shell is formed on the pattern and carrier the low melting point material within the shell is fused while the shell is supported with the carrier beneath the pattern so .that the fusible material within the shell can be drained rapidly past the carrier to free the shell from the carrier and carry with it any infusible particles which may be mixed with the low melting point material employed in forming the pattern. The empty shell then provides a casting cavity in the portion thereof. formed around the pattern, a recessed receiving portion for molten metal in the portion thereof formed about'the carrier and spaced gates in the portion thereof formed around the risers that connect the recessed portion with the casting cavity.

The mold is preferably in the form of a relatively thinwalled shell of refractory material and this shell is formed on the pattern and carrier assembly by dipping the assembly in a ceramic paste of the proper consistency to form a relatively thin layer of ceramic material on the pattern,

risers and carrier. In order to form a more uniform coating, the pattern and carrier assembly may be dipped repeatedly in the ceramic paste and turned during the intervals between dipping. After the shellis freed from the pattern and carrier it maybe inspected and repaired or reinforced by application of additional material to the exterior thereof if desirable and then baked at a high temperature to provide a refractory mold with a glazed or vitreous interior surface.

Various low melting point materials may be employed for the pattern, risers and carrier covering layer. Fusible waxes and plastic compositions that can be molded to the desired shapes and that have the requisite strength and various low melting point metals and alloys that have good casting characteristics may be employed.

The method of the present invention is particularly applicable to the making of molds for castings of intricate design which require patterns formed of a series of separately molded or cast sections such as molds for turbine wheels. In forming patterns for such molds in accordance with the present invention, the portion of the pattern that conformes to the apertured peripheral portion of the wheel is made up of a series of castings, each conforming to an arcuate peripheral portion of the wheel which includes one of the vanes. These castings each have arcuate outer'portions that abut end to end to form a continuous peripheral rim and arcuate inner portions that abut'end to end to form a continuous inner ring inwardly of the vanes. Each section has a vane that is inclined with respect to the top and bottom faces of the section and that is integrally joined to the arcuate inner and outer portions of the section. In order to provide a'firm weld between the sections, each section has end faces inclined in the same direction as the vanes, which provide relatively large areas of contact between the ends of adjoining sections. The arcuate sections are welded together in an assembly rack by subjecting the end faces to be joined to heat sufficient to bring the surfaces close tothe fusion temperature and pressing the abutting faces together while the sections are held in proper relative positions in an arcuate channel. The assembly rack is formed with a circular channel in which the arcuate pattern sections have a sliding fit and the rack has a sectorshaped movable section which contains a part of the circular channel. The sections are joined end to end in the arcuate channel. A number of sections are first joined together and placed in the movable sector which is supported in a retracted position, and the remainder of the sections are then assembled in the stationary portion of the rack, after which the two sections of the rack are brought together to join the parts of the annulus carried by the two sections of the rack and complete the assembly of the arcuate sections in a closed annulus. After the peripheral portion of the pattern is formed, a cast ring of the low melting point material conforming to the body portion of the wheel to be cast is welded to the inner ring of the annulus formed by joining the arcuate sections to complete the pattern.

The annular-pattern so formed is attached to a. carrier that has aring-shaped attaching portion formed of a material of a melting point higher than that of the pattern and having a covering layer of low melting point material that has been applied thereto in a suitable manner such as by molding or casting. The risers connecting the pattern to the carrier may becast integral with the pattern parts and these risers are preferably equiangularly spaced to form gates connecting the casting cavity to the annular pouring channel formed by the investing material about the'carrier. I

Objects of the invention are to provide a method of forming molds by investment vof a fusible pattern in 3 which the assembly and handling of the fusible pattern is simplified and in which the fusible pattern is protected against distortion during the pattern assembly and investment operations, to provide a method in which the pattern is fused and drained from the investing shell 'in such manner as to completely empty the shell 'and'wash out fractory mold by the investment of a fusible pattern with ceramic material.

Reference should be had to the accompanying drawings forming a part of this specification, in which:

Figure 1 is a plan view of one of the molds for casting an arcuate pattern section, showing the hinged inold' parts in closed position and the casing. cavity in dotted lines;

Fig. 2 is a side elevation of the closed the mold cavity in dotted lines;

Figs. 3, 4, 5 and 6 are plan views of four differently shaped arcuate sections that are separately cast and that are joined together to form a part of a complete annular pattern; I

Fig. 7 is a plan view of a ring-shaped casting. that forms part of the completed pattern;

mold showing Fig. 8 is a plan view of an assembling rackv employed to join the arcuate pattern sections together;

Fig. 9 is a radial section taken on the line indicated at it 9-9 in Fig. 8;

Fig. 10 is a plan view of the movably mounted sector that forms a part of the assembly rack;

Fig. 11 is a fragmentary side elevation. of a portion of and with the pattern sections joined end to end in a.

closed annulus;

Fig. 13 is a fragmentary radial section taken on the line indicated at 13-13 in Fig. 12;

Fig. 14 is a plan view showing, the cast ring that conforms to the body of the wheel to be cast joined to the assembled arcuate sections to complete the pattern;

Fig. 15 is a section taken on the line indicated at 15-15 in Fig. 14;

Fig. 16 is a plan view of the carrier to which the an.- nular pattern is attached prior to the. investing operation;

Fig. 17 is a side elevation of the carrier partially broken away to show the covering 'layer of fusible material by meansof which the carrier is attached to the pattern;

Fig. 18 is a side elevation of the pattern and carrier assembly, a portion of the carrier and' pattern. being broken away to show the pattern and the carrier rings attached thereto in radial section;

Fig. 19 is a fragmentary side elevation showing, the carrier pattern assembly supported for the dipping operation;

Fig. 20 is a fragmentary radial section through the pattern carrier. and ceramic shell after the ceramic. mate-' rial has been removed from the sides of thecarrier rings that face away from the pattern;

Fig. 21 is a side elevation showing the carrier pattern assembly supported on the carrier during the melting operation;

Fig. 22 is a plan view of a completed mold; Fig. 23 is a fragmentary radial section taken on the line indicated at 23-23 in Fig. 22;

Fig. 24 is a plan view of a turbine wheel cast in the mold;

Fig. 25 is a section taken on the radial line indicated at 25-25 in Fig. 24; and

Fig. 26 is a section taken on the arcuate line indicated at 26-26 in Fig. 24.

In Figs. 3, 4; Sand 6 of the. accompanying drawings, castings 1, 2, 3 and 4 are shown, each of which conforms to an arcuate portion of a turbine wheel for which a mold is to be'made. Each of these sections has arcuate inner and outer portions 5 and 6 that are connected by a thin vane 7. The vanes 7 of the sections 1, 2, 3 and 4 are all inclined in the same. direction. with respect to the bottom faces of the sections and the opposite ends of the inner arcuate portions 5' have inclined end faces 8 that are inclined in the same direction as the vanes 7. The outer arcuate portion 6 of each section has inclined end faces 9 that are disposed. in the planes of the end faces 8 of: the inner arcuate portion 5. The end. faces: 8 and 9 of each section are. spaced from. the vane 7 thereof and are adaptedyto contact throughout their entire extent with corresponding end faces. of adjoining sections when the sections are assembled in the annular. pattern. Y

The arcuate section 1 has a riser 11 projecting upwardly from its outer arcuate portion, 6 and the sections 2, 3 and 4 have correspondingv risers 12,13 and 14. A suitable number of arcuate sections 1, 2-, 3 and 4. are joined together to form the. peripheral portion of an. an nular pattern which conforms to the apertured peripheral. portion of the turbine wheel to be cast and the pattern also includesa ring 15'of low melting point material which conforms to the body portion of the; turbine wheel. The ring 15 may be provided with circu-mferentially spaced risers 16.

Each of the arcuate pattern sections may be cast. in a. mold suchas shown in Figs. 1. and 2v which has a base member 17 that has a fiat bottom; recess 18 with. acircular I peripheral wall 19 Within. which. mold sections: 20' and 21 have a sliding fit. The mold sections 20 and 21 swing on a central pivot 22 and meet on a radial parting line.'.

The two sections of each mold have cavities: 23 and 24 which conform to, the arcuate portions. 5 and 6v of one of the pattern sections and filler plates 25. and 26 mount ed in these cavities provide. core members between which.

the vane 7 of'the section is formed. Each mold is. pros vided with a pouring opening 27 and the two sections have. handles 28 by means of which they can be moved to and from closed position.

As herein shown. the peripheral portion of the. patternis formed by fifteen arcuate sections. As shown in Fig. 12, the pattern annulus has, three segments each. con sisting of two of the sections, 1, a single section 2,, a single section 3' and a single. section 4. These: fifteen sections are joined togetherto form the complete annulus in. an assembly rack such as? shown in Figs. 8 to 15 inclu-.-

sive. As herein shown this assembly rack has a base. plate 29 to which is permanently attached an assembly plate 30 which forms the major portion of a circular form for positioning the pattern sections. A radial track 31 is provided on the base platev 29 andv a sector plate 32 is slidably mounted on the track 31. The, stationary po-- sitioning plate 30 has a sector shaped. recess to receive the sector plate. 32 which engages the. plate 30 on radial parting lines 33. A circular positioning channel 34 is formed in the plates 30 and 32 in which thearcuate sections 1. 2, 3 and 4 have a sliding fit. A positioning block 35 is detachably mounted on the base plate 29 whenthe sector plate 32 is in retracted, position. The block 35 extends across an end of the channel 34 at one of the parting lines 33 and this block has an inner end portion that fits against theradial track 31 and is held in fixed position by suitable means such as a dowel pin 36. As shown in Fig. 8, the'block 35 has a beveled face 37 against which the end faces 8 and 9 of the inner and outer arcuate pow tions of a pattern section fit.

In assembling the arcuate sections in the channel 34, one of the sections is placed in engagement with the beveled face 37 of the positioning block 35 and the other sections are then placed together end to end in abutting relation in the channel 34. Prior to assembly of the arcuate sections in the channel 34, the end faces of the sections are brought to a temperature near the fusion point so that the sections willbe welded together when the inclined faces are pressed together. When the low melting point material of which the pattern sections are formed is mercury, a mercury amalgam, or a low melting point alloy containing mercury, the surfaces to be welded can be heated to the desired temperature by exposing them for a short period of time to air maintained at a temperature above the fusion point of the metal.

In forming an annulus from the arcuate sections, a sufficient number of the sectionsto fill the portions of the channel 34 in the sector plate 32 may be joined together in the channel of the stationary plate 30 and transferred to the sector plate 32, where they are supported as shown in Fig.10 of the drawings. A sufficient number of sections may then be joined together in the portion of the channel 34 in the stationary plate 30 to fill the same, after which the sector plate 32 may be moved radially into engagement with the plate 30 to join the sections into a complete annulus, as shown in Fig. 12 of the drawmgs.

An inner circular positioning plate 38 is provided that has a beveled peripheral edge 39 that borders the inner side of the channel 34 and the inner arcuate portions 5 of the pattern sections have inclined shoulders 40 that fit on the beveled edge 39. The positioning plate 38 has a peripheral recess 41 in which the ring fits and the ring 15 is provided on its under side with, a V-shaped rib 42 that fits in the annular V-shaped channel formed by the beveled edge 39 of the positioning plate 38 and the inner faces of the arcuate portions 5 of the pattern sections. The sector plate 32 has an inner end face that engages the stationary plate 30 on a parting line 43 'at right angles to the radial track 31, and the inner positioning plate 38 has a segment 44 thereof that is mounted on the sector plate 32.

After the arcuate sections have been assembled as shown in Fig. 12, the ring 15 is placed on the positioning plate 38 as shown in Figs. 14 and 15 and is welded to the inner ring of the annulus formed by the arcuate sections which it contacts throughout its circumference. The ring 15 and the annulus formed by the arcuate sections provide an annular pattern of low melting point material that conforms to the casting cavity that is to beformed in the mold.

In order to prevent distortion or marring of the pattern during the operations incident to the investment of the pattern with the mold forming material, the pattern is rigidly supported by a suitable carrier which also serves to form the pouring portion of the mold. As shown in Figs. 16, 17 and 18, the carrier has a rigid ring shaped attaching portion to which the pattern is joined, which may comprise inner and outer concentric rings 45 and 46 when the pattern has concentric rows of risers as herein illustrated. The inner ring 45 is of a size to overlie the risers 16 on the ring 15 and the outer ring 46 is of a size to overlie the risers 11, 12, 13 and 14 that are formed integrally with the arcuate sections of the pattern. The rings 45 and 46 are supported in concentric relation with their upper faces in the same plane by means of a framework which is formed by an annular row of posts 47 and 48 embedded in or otherwise attached at their lower ends to the rings 45 and 46, concentric metal rings 49 and 50 welded to the upper ends of the posts 47 and 48, and radial arms 51 welded to the top faces of the rings 49 and 50. The rings 45 and 46 and the framework supporting the same are formed of a metal of a higher melting point than the material forming the pattern. For example, the rings 45 and 46 may 16, ,three radial arms 51 are provided and these arms are equiangularly spaced, each arm projecting radially outwardly past the outer rings 50 and having downturned ends 52 which terminate in suspension eyes 53 adapted to receive the hooks of a suitable hoist. The eyes 53 are positioned below the top faces of the rings 45 and 46 to provide suspension points substantially in alinement with the center of gravity of the carrier and pattern assembly when the assembly is suspended from one or more of the eyes 53. In order -to enable the carrier to be welded to the risers of the pattern, a covering layer 54 of fusible material may be formed on the rings 45 and 46 by casting or other suitable means.

The top faces of the risers 11, 12, 13 and 14 are made flat and lie in the same plane and the risers 16 also have flat top faces in a single plane, so that the low melting point covering material on the rings 45 and 46 has an adequate area of contact with the risers to provide a firm weld, securing the pattern to the carrier. After the pattern is attached to the carrier, the carrier and pattern assembly is suspended from a, suitable hoist by engaging.

the hoist chain hooks to one or more of the suspension eyes 53 to support the pattern carrier assembly with the axis thereofv substantially horizontal as shown in Fig. 19. So supported the carrier and pattern assembly is dipped in a ceramic paste bath of a consistency such that the ceramic material will adhere in a thin layer on the sur- 51 to a hoist chain attached to another of the carrier arms.

After a shell of the desired thickness is obtained on the assembly, the ceramic materialis removed from the flat sides of the rings 45 and 46 that face away from the patternas shown in Fig. 20. The assembly is then supported on the carrier with the pattern above the carrier and while the assembly is supported in this position heat is applied to the low melting point material within the shell to fuse the same as shown in Fig. 21, the heat being applied to the exterior of the shell by placing the assembly in an atmosphere at a temperature above the melting point of the material forming the pattern and the covering layer on the carrier rings. This causes the portions of the fusible material contacting the interior of the shell to fuse first and, since the covering layer 54 is a relatively thin layer, the melting of this layer on the interior and exterior peripheries of the rings 45 and 46 opens channels for a drainage of the fused pattern forming material from the shell. As the pattern fuses the shell settles onto the rings 45 and 46 as shown in Fig. 21. Any fused material trapped in the shell will flow out simultaneously throughout the circumference of the cavity formed by the pattern when the shell is lifted off the carrier. By reason of the free discharge of fused material, any infusible residue which may be mixed with the material forming the pattern will be washed out of the shell, leaving the interior of the shell free from any impurities which might cause imperfections in the interior surface of the shell upon subsequent baking thereof to form a refractory mold.

During the fusing of the pattern the shell is supported sothatit can be lifted bodily ofi the carrienafter which itais' baked at a-high temperature to-provide a refractory mold with smooth'glazed or vitreous internal surfaces.

As shown=in Figs; 22 and 23,-the mold'so-formed-has a mold cavity with-circumferentially continuous inner and outer portions 56- and 57 which confor'mto thebody and rim ofthe, turbine wheel." The portions56 and57 are connected by# narrowelongated passages 58 which conform: tothe vanesof the turbine. Above the casting cavity the mold has inner and' outer circumferentially continuous pouring channels 59- and 60 which were formed about the carrier-rings 45 and 46.- Theichanneb 59 is connected with the inner portion 56' of the casting cavity by gates 61' that were: fOrmedLabOut the= risers 16 of the pattern ring ISabout Which the portion 56 of the moldicavity was formed. A-pouringchannel fitl is connected to the outer portion 57 'of'the casting cavity by circumferentiallyspaced gates 62 that were formed about the-risers 11, 12, 13 and 14extending-upwardly from-the portion of the'pattern' about which the portion 57 ofthe casting cavity was formed. In pouring the casting, moltenmetal may be simultaneously poured into the channels .591 and. 60 to'rapidly'fill theeircumferentially continuous'portions 56-and 57 of the casting cavity andfthe metal from: the portions 56 and 57 of the cavity will quickly fill'the vane'forming portions 58 of the casting.

duction of'other typesofcastings, particularlycastings offintricate design requiring2built uppatterns'; The design of the carrier andthe arrangement of. risers'canbe varied toaccommodate' the particular: casting for which the mold is being made.

It is to be understood that in accordance with the provisions 'of the patent statutes,- variations and modifications. of' the specific devices herein shown and described'may' be made without-departing from thespiritof .the invention'.

What I claim is:

l. The herein described methodtof forming frangible refractory one piece casting molds which comprises forming a pattern of low melting point material, applying a covering layer of low'melting point material on a carrier member that is of a size to overlie the major portion of one side of the pattern, joining said-carrier to said pattern by means ofspaced risers OfIiOW melting pointma terial that'are integrally joined to the pattern and to the covering layer on said carriermember, dipping said pattern and carrier member in aceramiczpaste to invest the pattern and. carrier in a shell .of ceramic material, removing ceramic material from the sideiof the. carrier memher that faces away from thepattern, melting the material forming the pattern, the risers and the covering layer while the shell is supported with the carrier member below the patternso as to drain'the low melting point material past-the carrier member and from the interior of the shellto free the shell from the carrier member, and baking said" shell. to form a'.frangible refractory mold having a casting cavity in theportion of the shell formed about the pattern; an open top'pouring channelin the portion. of the shell formed about the carrier member and gates connecting the pouring. channel and casting cavity in the portion of theshell formed about the risers.

2. The herein-described method of forming frangible refractory one piece casting'molds which comprises formingpa pattern '.of'low'melting:point material, applying a coveringvlayersof'rlow melting point material on a carrier member that is of Pa size to roverlie the major portion' of L one side *of the pattern; joining said carrier-to "said" pattern by means of sp'acedrisersof low-melting pointma terial that are integrally joined-tothe patterna'nd toth'e" covering layer on said carrier member, supporting the pattern on the carrier, repeatedly dipping thecarrier and pattern inaceramic pa'steand imparting turning move:- ments to the carrier and pattern between dippings'to" invest said p'attern' and c'arrier' in ashell-of ceramic ma terial' tha t isofsubstantially uniform thickness, remov ingceramic material fromthe side' of the'carrier member thatfaces away from the-pattern, melting the low melt ing point rnaterial while the patternis supported on the carrier member and ab'ove the sa'm'e to drainthe'fused material from-the shell past saidcarrier member to free the shell from th'e carrier member, and-baking said shell-- to form a frangible refractory mold having a casting cavity in the portion oftlie-shell formed aboutthepat tern; a pouringchannel intheportion'of the she'll'forr'ne'd' about the carrier member and 'ga-te's connectingtliepoun' ing 'channel -a nd castingcavi'ty 'in the portion of the shell formed about the risers: I

3i The herein described method offorming frangible molds for annular castingswhicl'i comprises forming an annular" pattern of low 'melting point material, applying a covering layer ofllow-melting point material on aca-rrier ring that is composed of 'amaterialof higher melting point, attaching said carrier ring to said pattern in axially spaced substantially coaxial relation and interposing between the pattern; and said covering layer 'a series of circumferential-13 spaced gate forming risers of low meltingpoint i material integrally joined to said pa-ttern-and said 'covering layer, investing the carrier ring 'and pattern :in a shell 3 of mold-able hardenable heat resistant investing material, rem'oving the inv'estingmaterial fronrthe 'si'de of thecarrier ring'thatffaces -away from thepat term; and fim'elting the materi'al forming the pattern,=- the i risers: and the-firingZcovering -layer while the shell l is-supportedt-with the carrierring below the pattern so ast'o drain the low 'm'eltin-g point'm'ateriabpast' saidring-and from: the interior of ithe .shell to freethe-shell from the 5 carrier ringer and provide a moldi having an annular-cast ing cavity in the portion of the shell formed about the pattern, an iopenmtop'ipouring annular channel in the portions.ofuthetshellformed about the carrier ring and gates connecting" the pouring channel'to -the casting cavity' in the portio'ns of the l shell formed about the risers.

4. The herein. described method I of i. forming frangible molds for'annular' castings which comprisesforming an annular pattern of low melting-point material thathas integral L circumferentially. spaced: risers 1 projecting I from one side thereof, applying a covering layer of low-melting: point material on a carrier ringithat is composed ofa materialiofhigher. melting point, attaching said carriei ringito said pattern .in axially spaced coaxial relation by integrally joining said-'covering layer to said-risers, invest ing the carrier ring,.patterni and risers in a shelliof moldable hardenable heat resistanttinvesting material, removing the investing material fromithe side of the-carrier ring that faces away from :the. pattern, and melting the material forming the pattern and said covering layer while theshell is supported. withthecarrier ring below 'thepattern so as to drain the :low meltingpoint material past said ring. to free the shell from'the carrier ring and provide a mold having an annular casting cavity, an open.

top annular pouring channel and circumferentially spaced:

gates connecting the pouring ,channelto the casting cavity. 5. The herein described methodof forming frangible molds for annular castin'gs'which comprises forming anw annular pattern of'low melting ipoint'metal, ,applying ja substantially coaxial relation and; inter-posing between the patternand said covering; layeria seriesofcircunn :ferentiallyspaced gateiormingcrisers oflow melting peinmi metal integrally joined to said pattern and said covering layer, investing the carrier ring and attached pattern in a shell of moldable hardenable heat resistant investing ma-' terial, removing the investing material from the side of the carrier ring that faces away from the pattern, and melting the metal forming the pattern, the risers and the carrier ring covering layer while the shellis supported with the carrier ring below the pattern so as to drain the low melting point metal past said ring and from the interior of the shell to free the shell from the carrier ring and provide a mold having an annular casting cavity in the portion of the shell formed about the pattern, an open top pouring channel in the portions of the shell formed about the carrier ring and gates connecting the pouring channel to the casting cavity in the portions of the shell formed about the risers.

6. The herein described method of forming frangible molds for annular castings which comprises forming an annular pattern of low melting point metal by casting a continuous ring and a series of arcuate sections and welding said arcuate sections end to end and to said ring, applying a covering layer of low melting point metal to a carrier ring of higher melting point, attaching the carrier ring to the pattern in axially spaced substantially coaxial relation and interposing between said pattern and said covering layer a series of circumferentially spaced gate forming risers of low melting point metal integrally joined to'said pattern and to said covering layer, investing said carrier ring and pattern in a shell of moldable hardenable heat resistant material, removing the investing material from the side of the carrier ring that faces away from the pattern, and melting the metal forming the pattern, the risers and the carrier ring covering layer while supporting the shell with the carrier ring below the patternso as to drain the low melting 'point metal from the shell past the carrier ring to free the carrier ring from the shell and form a mold having an annular casting cavity, an annular open top. pouring channel and a series of circumferentially spaced gates connecting said pouring channel to said cavity.

7. The herein described method of forming frangible molds for annular castings which comprises forming an annular pattern of low melting point metal that has integral gate forming risers projectingfrorn a side face and spaced apart circumferentially, casting a covering layer of low melting point metal on a carrier ring that is composed of a material of higher melting point and that is of a size to overlie said annular pattern, welding the metal covering layer on the inner side of said carrier ring to said risers, dipping said carrier ring and pattern in a ceramic paste to invest the same in a shell of ceramic material, removing the ceramic material from the outer side of said carrier ring, and melting the metal forming the pattern and the covering layer on the carrier ring while the.

shell with the pattern andcarrier ring therein is supported with the carrier ring beneath the pattern so as to drain the low melting point metal past said ring and from the interior of said shell to free the shell from the carrier ring and provide a mold having an annular casting cavity in the portions of the shell formed about the pattern, an open top, annular pouring channel in the portion of the shell formed about said carrier ring and a series of gates connecting the pouring channel and casting cavity in the portions'of the shell formed about said risers.

8. The herein described method of forming frangible molds for annular castings which comprises forming an annular pattern of low melting point metal that has integral gate forming risers projecting from a side face and spaced apart circumferentially, casting a covering layer of low melting'point metal on a carrier ring that is composed of a material of higher melting point and that is of a size to overlie said annular pattern, welding the metal covering layer on the inner side of said carrier ring to said risers, supporting said carrier ring and attaehed pattern withthe ring axis substantially horizontal,

intermittently dipping said ring and pattern in a ceramic paste bath to cause the ceramic material toadhere therev to and form an enclosing ceramic shell, imparting turning movements to said ring and pattern about the axis of the ring between dippings to cause a more uniform distribution of the ceramic material in the shell, removing the ceramic material from the outer side of the carrier ring, and melting the metal forming the pattern and the carrier ring covering while the shell is supported with the carrier ring beneath the pattern so as to drain the low melting point metal past said carrier ring and from the interior of said shell and provide a mold having an annular cast ingcavity, an open top annular pouring channel overlying the casting cavity and a series of gates connecting said channel to said cavity.

9. The herein described method of forming frangible molds for annular castings which comprises forming an annular pattern of a low melting point metal that has inner and outer substantially concentric circumferential rows of integral risers projecting from one side face thereof, casting covering layers of a low melting point metal on two carrier rings formed of a material of higher melting point, one of a size to overlie one row of risers and the other of a size to overlie the other row of risers,

Welding the covering layers on the inner sides of said carrier rings to said rows of risers, dipping said carrier rings and the attached pattern in a ceramic paste to invest the carrier rings and pattern in a shell of ceramic material, removing the ceramic material from the outer sides of said rings, and melting the metal forming the pattern and the ring covering layers while supporting the shell with the carrier rings beneath the pattern so as to drain the metal from'the interior of the shell past saidv rings to free the shell from said rings and form a mold having an annular casting cavity and two inner and outer annular pouring channels overlying the cavity and connected by gates to the cavity.

10. The herein described method of forming frangible molds for annular castings which comprises forming an annular pattern of a low melting point metal that has inner and outer substantially concentric circumferential rows of integral risers projecting from one side face thereof, casting covering layers of a low melting point metal on two carrier rings formed of a material of higher melting point, one of a size to overlie one row of risers and the other of a size to overlie the other row of risers, welding the covering layers on the inner sides of said carrier rings to said rows of risers, supporting said carrier rings with the pattern attached thereto with the axis of the rings substantially horizontal, dipping the rings and attached pattern while so supported repeatedly in a ceramic paste bath and imparting turning movements about said axis between dipping operations. to

form a ceramic shell about said pattern and rings, removing the ceramic material from the outer side of said rings, melting the metal of the pattern and carrier ring covering. while the shell is supported with the carrier rings beneath the pattern to drain the metal from the shell past said carrier rings to free the rings from the shell to provide in the shell an annular casting cavity, a pair of annular pouring channels overlying the cavity and connected thereto by spaced gates, and baking said shell to provide a refractory mold.

ll. The herein described method of forming frangible refractory one piece casting molds which comprises casting a series of pattern sections each composed of a low melting point metal and certain of the sections having integral risers projecting therefrom, welding said sections together to form a pattern with a series of risers projecting from one side thereof, casting a covering layer of low melting 'point metal on a carrier member composed of a metal of a melting point higher than that of the pattern and of a size to overlie said risers, welding said covering layer to said risers to attach the pattern ma mas tothe carrier, dipping said pattern and carrier member ir'ra-ceramic paste to invest the pattern and'carrier mem her in'a shell'of ceramic material, removing the ceramic material from the side of the carrier member facing away fromthe pattern, melting the metal forming the pattern, risersand'covering layer while the shell is supported with the'carrier member beneath'the pattern so as to drain the fused metal from the shell past said carriermember to free'the shell fromthe'ea'rrier-member, and baking said shell toforr'n a frangible refractory mold havinga'casting cavity in the portions thereof formed about the pattern, a pouring channel 1 in the portions thereof formed about the carrier member and gates'connecting' the pouring channel to the casting cavity" in the portions thereof formed about the risers.

12. The her'ein'described'method of forming frangible refractory one piece casting'moldswhich comprises casting a series of pattern sections each composed of a low melting point material, said sections having end faces in'clined to the upper and lower sides of the'sections and risers projecting from their upper sides, welding the sections together to formthe pattern 'by heating the inclined faces to near the fusion-point of the material and pressing the inclined faces'together, casting a covering layer of low melting point materialon a carrier member of a size tooverlie said'risers and welding'and attaching said carrier member to the patternby welding said covering layer to'said risers, dipping the pattern and carrier member in a ceramic'paste to investthe same in a shell of ceramic material, removing the ceramic material from the side of the carrier member facing away from the pattern, supporting the shell with the carrier member beneath the pattern'and'melting-the material of the pattern, the risers and-the covering layer to drain the material'fro'm the-shell and free the shell from the carrier member, and bakings'aid'shelll 13 The herein described method of forming frangible moldsfor annularcastings whichcomprises forming an annular pattern by casting a low melting point metal to form a series ofseetions that conform to arcs of an annulus, casting a circumferentially continuous ring with spaced gate forming risers projecting from a'face thereof,-iwelding said sections together 'endto end and to said annulus to form a pattern, casting a covering of low melting'point metal on a carrier ring formed of material of 'a" higher'melting point and that is of a size to overlie said risers, welding't'n'e covering layer on the inner side of said carrier ring to said risers to attach saidcarrierring to said pattern, dipping said carrier ring and pattern in a ceramic paste to invest the same in a shell of ceramic material, removing the ceramic materia'l-from the outer side of said carrier ring, and melting the'metal forming the pattern and'carrier ring coveringrlayer while said shell is supported-with the carrier ring'on the under side thereof so as'to drain the metal from the interior of the shell past said' carrier ring to free the shell from said ring and provide a mold having an-Iannular casting cavity in the portions of the shell formed about said pattern, an open top annular pouring channelin the portions of the shell formed about the carrierring and a series of gates from said pouring channel to said cavityin the portions of the shell formed about said risers.

14: The herein described method of forming a mold forjaturbine wheel or the like that has passages closely spaced-circumferentially adjacent its periphery that ex tend therethrough atan inclination to the plane of the wheel and that are separated by thin inclinedvanes which eomprises-formingan annular pattern of ailow melting point metalwhich conforms to the apertured peripheral portion ofthe turbine wheel and which has circumfe'n' entiaily'spacedgate forming risers projecting'from one side face, applying :a covering layer: of low melting. point metal toacarrier ring-of .a nietalof higher nieltingpoint and welding the covering layer on the inner side face of tern and carrier ringtherein is supported with the carrier ring oiith'e under side" thereof so asto drain the metal past the'car'rier ring and from the interior of theshell tofree the shellfrom said ringfiand'provide a moldhav ingan'ann'u'lar casting cavity in the portion of the shell formed about said pattern, an open top annular pouring, channel in the portion of the shell formed about'said' carrier ring and-a series of gates" formed by portions of the'shell formed about saidrisers and connecting said pouring channel and-said cavity.

15. The herein described method of forming a mold for a turbine'wheel or the like that'ha's a' ci'rcumf'erem tially' continuous peripheral portion and passages therethrough adjacent the periphery that are inclined to the plane of the Wheel and' that are separated by thin inclined vanes which comprises forming anannular pa'tA tern of a low melting, point metal that conforms to the apertured peripheral portion and to the body offthe wheel inwardly of the vanes and having circumferentially' spacedgate forming risers' projecting from a side face thereof casting a'co'vering layer of low melting point metal on a carrier ring formed of material having a" higher melting point and that is of a size to overlie said" risers, welding the inner face of said carrier to said risers,

dipping said carrier'ring and'pattern-in a ceramic paste, to invest the same in a shell of ceramic material, 'removing ceramic material from the outer face of said' rii g, supporting said'pattern carrier ring and shell with v .the carrier'rin'g on the under side, melting the metal forming the pattern and the carrier ring coveringland draining the metal from the shell'past'said carrier ring. to free the shellfrom the carrier ring and to form a mold having an annular casting cavity, a circumferen! tially continuous pouring channel overlying the cavity and a series of circumferentially spacedgates connecting said channel to said casting cavity.

16. The herein described method of forming a mold for a turbine wheel or the like that has a circumferene tially continuous peripheraltportion and passages therethrough adjacent the periphery that are inclined to the planeof the wheel and that areseparated by thin in-, clined vanes which comprises forming an annular pat tern conforming to the peripheral vaned portion of the wheel and having an inner circumferentially continuous portion conforming to the body of the wheel inwardly of. the vanes and having inner and outer rows of cirfcumferentially spaced risers projecting laterally in the same directionfrom said inner and peripheral portions",

castinga covering coating of low melting point metal;

on two carrier rings one of a size to overlie the risers of the outer-row and the other ofa size to overlie the risers of the inner row, Welding the covering onthe inner sides of one carrier ring to the risers of the outer row, welding the covering on the inner side of the other carrier rowto the risers of the inner ring, dipping the carrier rings with the attached pattern in a ceramic pasteto form a shell of ceramic material enclosing thecarrier 7 rings and pattern,.melting.the metalof the pattern and carrier ring coverings while the shell is supported-with the carrier rings beneath the pattern so as to drain the metal from the shell and pastthelcarrier rings to free the rings-and form a mold havingan annular casting. cavity and two annularpouringchannels overlyingtthel cavity and connected thereto byv spaced gates.

17. A- carrier for supporting. an annular pattern or low melting point metal for dipping in a bath of' shell. forming material comprising a castmetal'ring, ascries of axially extendingtmetal posts having their innertends attachedat' circumferentially spaced' points to Saidtasf? metal ring, a'metal 'snp erting'ring welded tsalid IJOSffi dipping said carrier ring and pattern ina ceramic paste to invest the same in a' shell 13 and disposed substantially parallel to said cast metal ring, and equiangularly spaced arms welded to said supporting ring, said arms extending radially and having end portions bent toward the plane of said cast metal ring and terminating in suspension eyes radially outwardly of said cast metal ring.

18. A carrier for supporting an annular pattern of low melting point metal for dipping in a bath of shell forming material comprising two substantially coaxial cast metal rings disposed one within the other in radially spaced relation with their outer faces in substantially the same plane, circumferentially spaced metal posts'having their inner ends attached to said rings and projecting axially outwardly therefrom, a metal supporting ring welded to the posts of each of said cast metal rings, said supporting rings being concentric and spaced outwardly from the outer faces of said cast metal rings, and equiangularly spaced radially disposed metal arms each welded to both of said steel rings and having outer ends bent inwardly and terminating in suspension eyes inwardly of said outer faces and spaced radially outwardly of said cast metal rings.

19. Apparatus for assembling arcuate sections end to end to form a closed annulus comprising a support having a top face provided with an open top circular channel of uniform width and depth throughout in which the sections to be joined have a sliding fit, said support having a fixed section and a movable section, said movable section being sector shaped and mounted for movement radially toward and away from the fixed section, said sections having radial parting lines that cross said channel, a positioning member engageable with said fixed section at one of the parting lines when the movable section is retracted and serving as a stop against which one of the arcuate sections to be joined may be engaged, said positioning member being removable to permit movement of the movable section into engagement with the fixed section and transfer of a series of joined arcuate annulus sections to the movable member and movement of the movable section into engagement with the fixed section to join annulus sections assembled in the portions of the circular channel in the fixed and movable support sections to form a complete closed annulus.

20. Apparatus for assembling in a closed annulus a series of arcuate sections of uniform radial width and having flat end faces that abut and that are all disposed at the same inclination to their bottom faces, a support having a top face provided with an open top circular channel in which said arcuate sections have a sliding fit, said support having a fixed section and a movable section that is sector shaped and that is movable radially toward and away from the fixed section, said movable section engaging said fixed section on radial parting lines that cross said channel, a positioning member cngageable with the fixed support section at one of said parting lines and having an inclined face against which an inclined end face of an arcuate annulus section will fit, said positioning member being removable to permit movement of the movable support member into and out of engagement with the fixed support member to permit transfer of a sufficient number of joined arcuate sections to fill the portion of the channel in said movable supportmember and to permit movement of the movable support section into engagement with the fixed support section to join arcuate assemblies of annulus sections on the two supports to form a closed annulus.

References Cited in the file of this patent UNITED STATES PATENTS 1,187,446 Moore June 13, 1916 1,335,509 Kralund Mar. 30 1920 1,478,495 Walther Dec. 25, 1923 1,584,638 Norris May 11, 1926 1,680,502 Craig et al Aug. 14, 1928 1,753,608 Kay 'Apr. 8, 1930 1,759,183 Bennington May 20, 1930 1,774,668 Reeder Sept. 2, 1930 2,193,750 Welker Mar. 12, 1940 2,204,123 Collins June 11, 1940 2,400,831 Kohl May 21, 1946 2,583,533 Hiensch Jan. 29, 1952 2,652,609 Sudia Sept. 22, 1953 FOREIGN PATENTS 479,671 Canada Dec. 25, 1951 OTHER REFERENCES Frozen Mercury Patterns, Steel, Allen, vol. 128, No, 12, pages 66-69 incl., Mar. 19, 1951, 

